This anatomical study stems from a preceding project (Z01 MH 00787- 08 LCS) in which it was shown in squirrel monkeys that a strip of midline frontal limbic cortex is involved in the spontaneous production of the separation call. The call ranks as a basic mammalian vocalization, serving originally to maintain maternal- offspring contact. The purpose of the present project is to define the respective connections of the frontal midline limbic and neocortex with the thalamus and other parts of the cerebrum. The two preceding reports dealt with the findings obtained with the use of WGA-HRP (wheat germ agglutinin conjugated to horseradish peroxidase) as a cytochemical tracer. In the present phase of the study fluorescent tracers for revealing double labeling of nerve cells are being used to assess the extent of thalamic innervation of midline areas by collateral nerve fibers. Injection of two different dyes into limbic and neocortical areas between frontal planes F22-F18 of the brain atlas revealed almost no evidence of double labeled cells in the thalamus. Another purpose of the study is to obtain information about cerebellothalamic relationships of the limbic "vocal area" and of the rostral supplementary motor area.